JP2753854B2 - Vertical continuous annealing furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a steel strip which has been heated without causing cooling wrinkles or shape defects even in the case of a thin steel strip during annealing of the steel strip. The present invention relates to a vertical continuous annealing furnace which can be gradually cooled and sufficiently cools a furnace body.

[Conventional technology]

Generally, a cold-rolled steel strip is continuously annealed to remove the effect of work hardening caused by cold rolling. Particularly in the case of a stainless steel strip, bright annealing is often performed to obtain a beautiful and high surface gloss. A conventional vertical continuous annealing furnace used for such continuous annealing will be described with reference to FIG. 4 by taking a bright annealing furnace as an example. In general, the vertical continuous annealing furnace 1 is configured such that an inlet seal portion 2, an inlet cut portion 3, a top roll 4, a heating strip portion 5, and the like from the upstream side of the running path of the steel strip S (the same position as the steel strip S shown in the figure). The structure is such that the annealing zone 6, the cooling zone 7, and the outlet-side sealing portion 8 are sequentially arranged (in this manner, the heating zone 5, the annealing zone 6, and the cooling zone 7 are arranged from above to below). Those arranged sequentially toward the bottom are called a down-heat system, and conversely, there is also an up-heat system arranged from below to above, but the present invention may employ any system. The heating zone 5, the slow cooling zone 6, and the cooling zone 7 are heated zone, annealing zone respectively.
A slow cooling zone and a cooling zone are formed.

The annealing of the steel strip S using such a vertical continuous annealing furnace (hereinafter, may be simply referred to as an annealing furnace) 1 is performed as follows. The steel strip S is passed through the inlet side seal part 2 into the annealing furnace 1, passes through the inlet side part 3, is changed in running direction by the top roll 4, and is heated.
Then, cooling is started from the slow cooling zone 6, cooled to approximately room temperature in the cooling zone 7, pulled out of the furnace from the outlet side seal 8, and the annealing is completed. The annealing zone 6 in the annealing furnace 1 in which such an annealing step is performed receives radiant heat from the heating zone 5 or radiant heat from the steel strip S heated to a high temperature in the heating zone 5. Therefore, if such measures against radiant heat are not taken, the inner wall plate 9 and the outer wall plate 10 of the slow cooling zone 6 are deformed by thermal strain or extend from the heating zone 5 to the cooling zone 6 side. Even if the furnace can 11 is heated red, the annealing furnace 1 itself may be damaged. Therefore, conventionally, as shown in FIG. 4, a plurality of water-cooled jackets 12 '
And a similar water-cooled jacket 12 is also provided in a partition wall 5a of the heating zone 5 from the slow cooling zone 6. With these water-cooled jackets 12, 12 ', the furnace body such as the inner wall plate 9, the outer wall plate 10, and the furnace can 11 of the slow cooling zone 6 is not damaged by radiant heat, and the annealing can be performed without any trouble. Was.

However, in recent years, ultra-thin materials and wide-width orientations have been increasing as high-tech steel sheets, and the demand for stainless steel sheets in particular has increased. To meet such demands, the following problems have been encountered with the conventional annealing furnace 1 as it is. there were.

Generally, the steel strip S is easily cooled in a short time as its thickness becomes thinner. However, in the steel strip S having a certain thickness or more, the cooling by the slow cooling zone 6 does not occur too much. However, when a steel strip S having a thickness of 1.0 mm or less, particularly an ultrathin steel strip S of 0.3 mm or less is passed through the annealing furnace 1, the amount of radiant heat from the steel strip S in the annealing zone 6 is small. The temperature of the slow cooling zone 6 cannot be maintained in an appropriate temperature range by the water-cooled jacket 12 ', so that the steel strip S is rapidly cooled. As described above, when the steel strip S is rapidly cooled in the initial cooling stage on the exit side of the heating strip 5, the cooling wrinkles 13 due to the cooling strain as shown in FIG. As shown in FIG. 2B, a shape defect that causes the shape of the steel strip S to bend into an arc shape occurs, and due to the shape defect, the steel strip S comes into contact with a furnace wall or the like, slips, and a surface flaw 14 occurs. As shown in FIG. 5 (c), the steel strip S having an arcuate shape and having an inferior shape is brought into contact with the rolls inside and outside the furnace while being tensioned, and is crimped or bent so as to be stretched in the width direction. The product may be severely degraded, for example, as if it were broken.

Therefore, while the rapid cooling of the steel strip S in the slow cooling zone 6 is prevented and the rapid cooling of the steel strip S is prevented, the protective cooling of the furnace body is weakened, the influence of radiant heat is increased, and the furnace body is damaged. Various measures such as those described below have been implemented to prevent this from happening, but new problems have arisen and have not been solved.

That is, one of them is a water-cooled jacket in the slow cooling zone 6.
In this method, 12 'is wrapped with heat insulating material to reduce the cooling capacity. However, in this case, it is not possible to wind or remove the heat insulating material depending on the steel type and dimensions (sheet thickness × sheet width) of the steel strip S to be passed and the passing speed, and the heat insulating material is kept at a high temperature for a long time. When exposed and deteriorated and scattered in the furnace, or when passing a thick steel plate S, the cooling capacity for the furnace body was insufficient.

The other is that when passing an extremely thin steel strip S, a part of the cooling gas is circulated from the cooling zone 7 to the slow cooling zone 6 so that the steel strip S is cooled slowly. It is a method of minimizing body cooling. However, in this case, it is difficult to control the temperature of the cooling gas to be circulated, and the convective cooling by circulating the gas tends to cause uneven cooling of the steel strip S, and wrinkles and shape defects due to uneven cooling are generated in the steel strip S.

Still another method is to heat the inner wall plate 9 with a heater. However, in this case, the equipment becomes complicated or energy for heating is required, thereby increasing the cost.

In addition, there has been a measure to strictly limit the thickness range of the steel strip S to be passed for each annealing furnace 1 to, for example, a thin material or a thick material, and to manufacture and use a dedicated furnace as appropriate, Such a dedicated furnace cannot be used for steel strip S other than its thickness,
Aligning various dedicated furnaces over a wide range of plate thickness has had problems in terms of cost, availability, and the like.

[Problems to be solved by the invention]

The present invention solves the above-mentioned problems of the prior art, and enables continuous annealing of a steel strip in a single annealing furnace regardless of the type and size of the steel, particularly the thickness of the steel sheet, and therefore, the steel strip having a small thickness can be passed through. It is an object of the present invention to realize continuous annealing of a steel strip by simultaneously preventing the overcooling in the annealing zone and sufficiently protecting and cooling the furnace body against radiant heat even when the steel strip is formed.

[Means for solving the problem]

As a result of various studies by the present inventors, the water-cooled jacket of the annealing zone in the conventional annealing furnace was abolished, and instead, a rectangular parallelepiped water-cooled jacket was installed in the annealing zone, and the traveling path of the rectangular water-cooled jacket and the steel strip was used. Use an annealing furnace with a heat-insulating plate attached to the heat-insulating plate, which is connected to a rectangular parallelepiped water-cooled jacket to conduct heat and to extend the working length of the slow cooling zone substantially. Thus, the present invention has been made by finding out that the above-mentioned problem can be solved.

Hereinafter, the vertical continuous annealing furnace according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is an explanatory view showing a cross section of an essential part of one example of a vertical continuous annealing furnace according to the present invention, and FIG. 2 is an essential part of one side of an annealing zone.
FIG. 3 (a) and (b) are enlarged perspective views showing the embodiment, and the relationship between the plate thickness (mm) of the stainless steel strip and the appropriate threading speed (m / min) and the corresponding plate thickness (m) in a usage example. FIG. 2 is a diagram showing a temperature (mm) and a heat insulating plate temperature (° C.).

In the vertical continuous annealing furnace 15 according to the present invention, each side of the annealing zone 6 across the running path of the steel strip S is constituted by the following members. That is, reference numeral 16 denotes a rectangular parallelepiped water-cooled jacket whose side cross section is rectangular as shown in FIG. 1 and whose larger cooling surface is provided on the lower surface of the partition wall 5a of the heating band 5 from the slow cooling zone 6. As shown in FIG. 2, the steel strip S is installed facing the running path of the steel strip S. Therefore, the side surface of the rectangular parallelepiped water cooling jacket 16, that is, the smaller cooling surface is parallel to the running path of the steel strip S. Reference numeral 17 denotes a temperature control body, the main part of which is the above-described rectangular parallelepiped water-cooled jacket as shown in FIG.
The steel strip S is provided so as to be located between the partition wall 5a of the heating strip 5 and the cooling strip 7 on the side of the traveling path of the 16 steel strips S. The temperature controller 17 includes a heat insulator 18 and a heat insulator 19, and the heat insulator 19 is connected to the heat insulator 18 on the side of the cooling zone 7. As shown in FIG. 1, the heat shield 18 has a heat shield 18a located at least between the side surface of the rectangular parallelepiped water-cooled jacket 16 and the running path of the steel strip S. The heat-insulating plate 18a has its front side facing the steel strip S and faces the surface of the traveling path of the steel strip S. The edge of the heating strip 5 side and the partition wall of the heating strip 5 are provided. A gap g for elongation is provided between the gap g and the gap 5a. Heat shield
Heat resistant steel such as SUS310 steel is used for 18a.
Further, the heat retaining body 19 has a heat retaining inner wall plate 19a as shown in FIG. The front side of the heat-retaining inner wall plate 19a is continuously provided at a position forming an opposing extension surface of the steel strip S and forming the same plane as the opposing surface of the steel strip S of the heat insulating plate 18a, and the back side thereof is provided with a heat insulating material 19b. It is kept warm. The heat-insulating plate 18a of the heat-insulating body 18 and the furnace can 11 extending from the heating zone 5 to the slow cooling zone 6 are connected to the rectangular parallelepiped water-cooled jacket 16 as shown in FIG. I have. As shown in FIG. 1, the furnace can 11 usually extends from near the outer peripheral surface of the furnace wall, and a support frame 20 supports the heating zone 5 inside the furnace can. In FIG. 1, one end of the temperature control body 17 is a partition wall of the cooling zone 7.
Although it is in contact with 7a, expansion and contraction due to temperature fluctuation can be freely performed by a gap g for the extension allowance provided at the end opposite to the cooling band portion 7 and a sliding portion (not shown) of each portion appropriately provided.

Next, one specific embodiment of the configuration of the slow cooling zone 6 as described above will be described. As shown in FIG. 2, a metal plate having a U-shaped cross section is used as the heat shield 18 so that its web portion is connected to the heat shield 18a.
The flange located on the side of the cooling band 7 is connected to the rectangular parallelepiped water-cooled jacket 16 on its inner surface so as to conduct heat. The heat shield 18 is attached to the heat shield 18 by the mounting plate 21.
It is firmly attached by being integrally connected to the rectangular parallelepiped water cooling jacket 16 using not only the web portion a but also the flange portion. As shown in FIG. 2, a metal plate having an L-shaped cross section is slidably overlapped on its web portion and used as a heat retaining inner wall plate 19a as the heat retaining body 19, and is opposed to the heat retaining inner wall plate 19a. The space surrounded by the elastic wall 19c provided at the position and the upper and lower flange portions is filled with the heat insulating material 19b. And this heat insulator 18
The heat insulator 19 and the heat insulator 19 are overlapped so that the heat shield plate 18a and the heat insulator inner wall plate 19a are on the same plane and face the traveling path of the steel strip S to form the temperature regulator 17. Also in this case, as shown in FIG. 2, the furnace can 11 is a rectangular parallelepiped water-cooled jacket.
Needless to say, it is connected to the heat conductive member 16.

(Operation)

(I) Regarding the action of preventing the furnace body damage due to the radiant heat in the slow cooling zone section 6: The partition wall 5a of the heating zone section 5 has the larger cooling surface of the rectangular parallelepiped water cooling jacket 16 of the slow cooling zone section 6 as the partition wall 5a. The cooling water is cooled by the conventional water-cooled jacket 12 in the partition wall 5a in the partition wall 5a, so that the cooling is performed over a wider area. Therefore, the influence of the radiant heat from the heating zone 5 side on the furnace body is reduced. Further, the radiant heat from the heated steel strip S is also transmitted to the rectangular parallelepiped water-cooled jacket 16 via the heat-insulating plate 18a provided between the steel strip S and the radiant heat leaked from the gap g for the extension. There is no problem because it is slight, but it is also blocked by the support frame 20 and the furnace can 11
Does not reach. Therefore, even if the steel strip S to be annealed is thin or thick, the furnace body is not likely to be damaged by radiant heat and the furnace body can be sufficiently protected.

(Ii) Regarding the slow cooling action of the steel strip S in the slow cooling zone section 6: An appropriate slow cooling rate after heating in annealing is, for example, 100 to 150 ° C / sec in the case of a stainless steel strip, and the heating temperature is about
Since the temperature is 1,100 to 800 ° C, the steel strip S in the annealing zone 6
If the temperature in the vicinity of the travel path is not considerably high, the steel strip S is rapidly cooled.

By the way, the water temperature of a water-cooled jacket is generally 10
Below 0 ° C, it is usually about 40-50 ° C. Therefore, if the steel strip S and the water-cooled jacket are directly opposed to each other, it is difficult to keep the cooling power of such a low-temperature water-cooled jacket in balance with the cooling rate of the water-cooled jacket and to satisfy an appropriate slow cooling rate because the temperature is hardly lowered and high. It is limited to a thick steel strip S to which thermal radiation is connected. In the vertical continuous annealing furnace 15 according to the present invention, a rectangular parallelepiped water-cooled jacket 16 is used as a water-cooled jacket, and the smaller side of the cooling surface is directed to the traveling path of the steel strip S, and the rectangular parallelepiped water-cooled jacket 16 is provided between them. By interposing the heat-insulating plate 18a connected so as to allow heat conduction, it is possible to keep the temperature of the heat-insulating plate 18a in a wide range from a low temperature to its heat-resistant temperature (usually about 800 to 1,100 ° C). Steel strip S
The threading speed (m / min) is adjusted in accordance with the temperature and the sheet thickness of the steel strip S.
The temperature of the heat-insulating plate 18a can be kept at an appropriate temperature by keeping the temperature from dropping to prevent rapid cooling and thereby keeping a large amount of heat radiation. When the passing speed is increased, the gradual cooling time is reduced accordingly, but in the vertical continuous annealing furnace 15 according to the present invention, the heat-retaining inner wall plate 19 is kept warm.
The slow cooling time is substantially extended and compensated by the fact that a is connected to the heat insulating plate 18a. Since the gradual cooling of the steel strip S in the gradual cooling zone portion 6 is mainly performed by radiant heat transfer, unevenness of the gradual cooling unlike the case of forced convection does not occur.

〔how to use〕

The plate thickness is 1.0 m using the vertical continuous annealing furnace 15 according to the present invention.
When the steel strip S thicker than about m is annealed, even when the steel strip S is passed at the same speed as in the case of using the conventional annealing furnace, it is not rapidly cooled in the annealing zone 6, and the protective cooling of the furnace body is also performed. There is no problem because it is enough. For the case where the plate thickness is 1.0 mm or less, preferably, the heat insulating plate 18a
The sheet passing speed for maintaining heat so as to maintain the temperature optimal for the slow cooling of the steel type of the steel strip S to be continuously annealed is determined, and the sheet is annealed by passing the sheet in accordance therewith. If the heat-insulating plate 18a still cannot be kept at an appropriate temperature even if the passing speed is maximized in the equipment, the problem of radiant heat control is no longer present and the steel strip S
The problem can be solved by adjusting the conditions of the cooling zone 7 together with focusing only on the quality of the cooling zone.

〔Example of use〕

Using the same annealing furnace 15 as in FIG. 1 having the main structure of the annealing zone 6 as in FIG. 2, stainless steel of various thicknesses of 1.5 mm or less (with a width of 1,000 to 1,300 mm). Steel strip S (SUS3
04:20 coil, SUS430: 20 coil), the temperature of the heat-insulating plate 18a is set to about 80 which is an appropriate temperature for annealing the stainless steel strip S.
As a result of performing a test while maintaining the temperature at about 0 ° C. or slightly higher and maintaining the heat while changing the sheet passing speed, the results shown in FIGS. 3A and 3B were obtained. According to the results, when the stainless steel strip S of SUS304 having a thickness of 0.1 mm and the above width range was passed through the plate at a speed of 37 m / min and annealed, the temperature of the heat insulating plate 18a could be maintained at about 900 ° C. As a result, the stainless steel strip S was sufficiently cooled gradually, and could be annealed without generating any cooling wrinkles, deformation defects, surface flaws or the like.

Except for the annealing zone 6, the relationship between the sheet thickness and the passing speed of the same stainless steel strip and the sheet thickness and the inner wall of the furnace when the same conventional annealing furnace 1 as the above-described annealing furnace 15 was used. 3 in (a) and (b) are indicated by broken lines. In this relationship, the stainless steel strip S having the same thickness of 0.1 mm was passed through the annealing furnace 15 at a passing speed of 25 m / min for the case of a thickness of 0.1 mm, but the generation of cooling wrinkles and the like could not be prevented. Was. Conversely, the steel sheet was passed through the conventional annealing furnace 1 at the speed of 37 m / min. However, the temperature of the stainless steel strip S reached the position of the furnace inner wall 9 at a high temperature of 900 to 1,000 ° C., and the slow cooling time was insufficient. Rapid cooling was performed and cooling wrinkles were observed.

〔The invention's effect〕

The vertical continuous annealing furnace according to the present invention described in detail above eliminates the water-cooled jacket of the annealing zone in the conventional annealing furnace, and instead installs a rectangular parallelepiped water-cooled jacket facing the heating zone, and By interposing a heat insulating plate between the steel strip running path and connecting the heat insulating plate and the furnace can body to a rectangular parallelepiped water-cooled jacket so as to conduct heat, and further connecting the heat insulating inner wall plate to the heat insulating plate, Protection of the body is sufficient even when passing through a thick steel strip, and even when passing through a thin steel strip and the amount of radiant heat is small, the effect of the cooling action of the rectangular parallelepiped water-cooled jacket can be reduced by the heat shield. It was possible to maintain the proper temperature by reducing the size and increasing the passing speed to maintain the heat of the heat insulating plate, and the decrease in the slow cooling time was compensated by the heat insulating inner wall plate connected to the heat insulating plate.

Thus, the vertical continuous annealing furnace according to the present invention is the same furnace.
Any steel strip up to a very thin plate thickness of about 0.05 mm can be annealed without generating cooling flaws and the like, and its industrial value is very large.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a cross section of an essential part of one example of a vertical continuous annealing furnace according to the present invention, FIG. 2 is an enlarged perspective view showing one embodiment of an essential part on one side of an annealing zone, and FIG. Figures (a) and (b) show the relationship between the stainless steel strip thickness (mm) and the appropriate threading speed (m / min), and the corresponding thickness (mm) and heat-insulating plate temperature (° C) in the usage examples. FIG. 4 is an explanatory view showing a cross section of a main part of one example of a conventional vertical continuous annealing furnace, and FIGS. 5 (a), (b) and (c) are slow cooling zones. FIG. 4 is a view showing a state in which wrinkles, shape defects, and surface flaws are generated due to rapid cooling in the embodiment. In the drawings: 1 ... Conventional vertical continuous annealing furnace 2 ... Inlet seal part 3 ... Inlet shout part 4 ... Top roll 5 ... Heating zone 5a ... Partition wall 6 ... Slow cooling zone 7 ... … Cooling band part 7a …… Partition wall 8 …… Outside seal part 9 …… Inner wall plate 10 …… Outer wall plate 11 …… Furnace can body 12 …… Water cooled jacket 12 '…… Water cooled jacket 13 …… Cooling wrinkle 14… … Surface flaw 15 ……………………………………………………………………………………………………………………………………………………………………………………………. … Insulation material 19c… elastic wall 20… support frame 21… mounting plate g… gap for extension

Claims (2)

(57) [Claims] 1. A slow cooling type vertical continuous annealing furnace in which a heating zone (5), a slow cooling zone (6), and a cooling zone (7) are sequentially arranged along a vertical steel strip running path. On each side of the strip (6) sandwiching the steel strip running path, the rectangular parallelepiped water-cooled jacket (16) divides the larger cooling surface with the partition wall (5a) of the heating strip (5) from the slow cooling strip (6). ) Is installed along the steel strip running path, and the temperature control body (17) is on the steel strip running path side of the rectangular parallelepiped water-cooled jacket (16) and is a partition wall (5a) of the heating strip part (5). ) And the cooling zone (7) are installed such that the main part thereof is located, and the temperature control body (17) is connected to the heat shield (18) and the cooling zone (7) side. And a heat insulating body (19). The heat insulating body (18) has a heat insulating plate (18a) located at least between the side surface of the rectangular parallelepiped water-cooled jacket (16) and the steel strip running path. -Proof hot plate if you are (18
In a), the front side forms a steel strip facing surface, faces the steel strip running path, and has a gap (g) for allowance for extension between the heating strip (5) and the partition wall (5a). The heat insulating body (19) has a heat insulating inner wall plate (19a) having a steel strip facing extension surface which is flush with the steel strip facing surface of the heat insulating plate (18a) of the heat shield (18). And a heat insulating material (19b) on the back side thereof, and a furnace extending from the heat insulating plate (18a) of the heat insulating body (18) and the heating zone (5) to the slow cooling zone (6). The can (11) and the rectangular parallelepiped water-cooled jacket (16) respectively
A vertical continuous annealing furnace (15), which is connected to the heat-conductive member so as to be able to conduct heat. 2. A heat insulator (18) made of a metal plate having a U-shaped cross section in which a web portion forms a heat shield plate (18a), and a metal plate having an L-shaped cross section can slide on the web portion. The heat insulation inner wall plate (19a) is surrounded by the heat insulation inner wall plate (19a), the upper and lower flange portions, and the elastic wall (19c) provided at a position facing the heat insulation inner wall plate (19a). Insulation material in the space (19
The heat insulator (19) filled with b) is overlapped to form a heat insulator (17), and the flange of the heat insulator (18) on the heat insulator (19) side is a rectangular parallelepiped on its inner surface. The vertical continuous annealing furnace (15) according to claim 1, wherein the vertical continuous annealing furnace (15) is connected to the water-cooled jacket (16) so as to be able to conduct heat.